U.S. Pat. No. 4,973,647, to Bretches et al., discloses the use of a 28-32 mole percent 2-methyl-1,5-diaminopentane (MPMD) component in a diamine chain extender mixture (with ethylene diamine) for preparing spandex based on poly(tetramethyleneether) glycol. However, when the MPMD content exceeds 32 mole % or falls below 28 mole %, respectively, physical properties such as break elongation and heat settability suffer and become unacceptable.
U.S. Pat. No. 5,000,899, to Dreibelbis et al., discloses a spandex made from a copolyether glycol of 3-methyltetrahydrofuran and tetrahydrofuran, an organic diisocyanate and a mixture of diamines, the mixture containing, e.g., ethylene diamine and a diamine coextender, e.g., 2-methyl-1,5-pentanediamine, the latter amounting to 20-50 mole percent of the total diamine mixture. However, this spandex must be heat-set at high temperatures generally utilized with commercial yarns containing 6-nylon fibers.
Japanese Published Patent Application 09-136937 discloses spandex based on copolyether glycols, organic diisocyanates, and mixtures of nonbranched linear aliphatic diamines with branched chain aliphatic diamines, the latter preferably less than 20 mole % of the total. When a 65/35 mole % mixture of ethylenediamine and 2-methyl-1,5-pentanediamine was used, there were found substantial high temperature set and problems in practical use.
There is still a need for spandex having a desirable balance of properties, that is, a spandex which can be heat-set efficiently at moderate temperatures and, simultaneously, provide a desirable balance of other physical properties such as low load power and high elongation.